Documents to be read by a document reading apparatus include those bound in book form. Such a document usually includes curved paper surface regions adjacent a joint. When this document is read for reproducing image data as it is, images adjacent the joint become compressed, resulting in distorted images.
A countermeasure to this inconvenience is disclosed in a Japanese patent application laid open under No. 62-143557. The prior apparatus disclosed in this publication comprises a line sensor for scanning and reading a document, and a distance sensor for detecting distances to a document surface. The line sensor is caused to read the document with varied pitches in an auxiliary scanning direction in accordance with distances detected during a reading operation.
However, the construction for effecting correction during a document reading operation is applicable only to an apparatus employing a scan type image reader. This construction has a further disadvantage of being unable to cope with curvatures in other directions than the auxiliary scanning direction.